Valgrind 在 boost::filesystem::path::parent_path() 上报告大小 8 的无效读取

Question

以下代码按预期工作，但在使用 valgrind 运行时会报告 "Invalid read of size 8" 错误。

#include <iostream>
#include <boost/filesystem.hpp>
#include <boost/program_options/options_description.hpp>
#include <boost/program_options/parsers.hpp>
#include <boost/program_options/variables_map.hpp>

namespace po = boost::program_options;

int main(int argc, char* argv[])
{
    po::options_description desc("Allowed options");
    desc.add_options()
            ("report,r", po::value<std::string>(), "single input image");
    po::variables_map vm;
    po::store(po::parse_command_line(argc, argv, desc), vm);
    po::notify(vm);
    if(vm.count("report")){
        boost::filesystem::path reportFile = boost::filesystem::path(vm["report"].as<std::string>());
        boost::filesystem::path reportPath = reportFile.parent_path();
        std::string reportParentPath = reportPath.string();
        std::cout << reportParentPath << std::endl;
    }
}

当使用参数 ./boostFilesystemTest -r folder/file.html 运行时，程序 returns 'folder'（如预期）：

valgrind 报告的内容：

==23831== Memcheck, a memory error detector
==23831== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==23831== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==23831== Command: ./boostFilesystemTest -r folder/file.html
==23831== 
folder
==23831== Invalid read of size 8
==23831==    at 0x63CEBC0: wcscmp (in /lib64/libc-2.15.so)
==23831==    by 0x5B9E4C3: std::moneypunct<wchar_t, false>::~moneypunct() (in /usr/lib64/libstdc++.so.6.0.17)
==23831==    by 0x5B9E548: std::moneypunct<wchar_t, false>::~moneypunct() (in /usr/lib64/libstdc++.so.6.0.17)       
==23831==    by 0x5B936B4: std::locale::_Impl::~_Impl() (in /usr/lib64/libstdc++.so.6.0.17)                         
==23831==    by 0x5B937EC: std::locale::~locale() (in /usr/lib64/libstdc++.so.6.0.17)                               
==23831==    by 0x636BC4E: __cxa_finalize (in /lib64/libc-2.15.so)                                                  
==23831==    by 0x5708272: ??? (in /usr/lib64/libboost_filesystem.so.1.49.0)                                        
==23831==    by 0x400EDDE: _dl_fini (in /lib64/ld-2.15.so)                                                          
==23831==    by 0x636B8B0: __run_exit_handlers (in /lib64/libc-2.15.so)                                             
==23831==    by 0x636B934: exit (in /lib64/libc-2.15.so)                                                            
==23831==    by 0x635545B: (below main) (in /lib64/libc-2.15.so)                                                    
==23831==  Address 0x6906668 is 0 bytes after a block of size 8 alloc'd                                             
==23831==    at 0x4C2A147: operator new[](unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so) 
==23831==    by 0x5B9E1A9: std::moneypunct<wchar_t, false>::_M_initialize_moneypunct(__locale_struct*, char const*) (in /usr/lib64/libstdc++.so.6.0.17)                                                                                 
==23831==    by 0x5B95BE6: std::locale::_Impl::_Impl(char const*, unsigned long) (in /usr/lib64/libstdc++.so.6.0.17)
==23831==    by 0x5B96689: std::locale::locale(char const*) (in /usr/lib64/libstdc++.so.6.0.17)                     
==23831==    by 0x571348E: boost::filesystem3::path::wchar_t_codecvt_facet() (in /usr/lib64/libboost_filesystem.so.1.49.0)                                                                                                              
==23831==    by 0x5714A34: boost::filesystem3::path::parent_path() const (in /usr/lib64/libboost_filesystem.so.1.49.0)                                                                                                                  
==23831==    by 0x405CDF: main (main.cpp:19)                                                                        
==23831==                                                                                                           
==23831== Invalid read of size 8                                                                                    
==23831==    at 0x63CEBC0: wcscmp (in /lib64/libc-2.15.so)                                                          
==23831==    by 0x5B9E3B3: std::moneypunct<wchar_t, true>::~moneypunct() (in /usr/lib64/libstdc++.so.6.0.17)        
==23831==    by 0x5B9E438: std::moneypunct<wchar_t, true>::~moneypunct() (in /usr/lib64/libstdc++.so.6.0.17)        
==23831==    by 0x5B936B4: std::locale::_Impl::~_Impl() (in /usr/lib64/libstdc++.so.6.0.17)                         
==23831==    by 0x5B937EC: std::locale::~locale() (in /usr/lib64/libstdc++.so.6.0.17)
==23831==    by 0x636BC4E: __cxa_finalize (in /lib64/libc-2.15.so)
==23831==    by 0x5708272: ??? (in /usr/lib64/libboost_filesystem.so.1.49.0)
==23831==    by 0x400EDDE: _dl_fini (in /lib64/ld-2.15.so)
==23831==    by 0x636B8B0: __run_exit_handlers (in /lib64/libc-2.15.so)
==23831==    by 0x636B934: exit (in /lib64/libc-2.15.so)
==23831==    by 0x635545B: (below main) (in /lib64/libc-2.15.so)
==23831==  Address 0x6906898 is 0 bytes after a block of size 8 alloc'd
==23831==    at 0x4C2A147: operator new[](unsigned long) (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==23831==    by 0x5B9DC19: std::moneypunct<wchar_t, true>::_M_initialize_moneypunct(__locale_struct*, char const*) (in /usr/lib64/libstdc++.so.6.0.17)
==23831==    by 0x5B95C33: std::locale::_Impl::_Impl(char const*, unsigned long) (in /usr/lib64/libstdc++.so.6.0.17)
==23831==    by 0x5B96689: std::locale::locale(char const*) (in /usr/lib64/libstdc++.so.6.0.17)
==23831==    by 0x571348E: boost::filesystem3::path::wchar_t_codecvt_facet() (in /usr/lib64/libboost_filesystem.so.1.49.0)
==23831==    by 0x5714A34: boost::filesystem3::path::parent_path() const (in /usr/lib64/libboost_filesystem.so.1.49.0)
==23831==    by 0x405CDF: main (main.cpp:19)
==23831== 
==23831== 
==23831== HEAP SUMMARY:
==23831==     in use at exit: 0 bytes in 0 blocks
==23831==   total heap usage: 539 allocs, 539 frees, 35,943 bytes allocated
==23831== 
==23831== All heap blocks were freed -- no leaks are possible
==23831== 
==23831== For counts of detected and suppressed errors, rerun with: -v
==23831== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 2 from 2)

我看不出这个 "Invalid read of size 8" 的来源以及如何修复代码。有人有想法吗？

我在 openSuse 12.2 上使用了 boost 1.49.0。

编辑

在使用 valgrind 测试时，使用 LANG=C 运行不会产生大小为 8 的无效读取。我不知道这是什么原因。

Answer 1

正如 sehe 评论的那样，这确实与语言环境有关。运行 LANG=C 使用 valgrind 测试时不会产生大小为 8 的无效读取。

Answer 2

放

::std::locale::global(::std::locale(""));

在 main() 的开头为我工作，我不再看到愚蠢的 valgrind 警告。

Answer 3

我猜测 wcscmp 的实现有花哨的代码，可以一次读取 8 个字节作为单个寄存器获取。它应该一次读取一个字节并在 [=11=] 处停止，但必须处理多字节字符并且不能过早停止。

Valgrind 在 boost::filesystem::path::parent_path() 上报告大小 8 的无效读取

Valgrind reports Invalid read of size 8 on boost::filesystem::path::parent_path()

c++

valgrind

boost-filesystem